The Species Information Index

An indicator for assessing biodiversity monitoring efforts

A frog with a light green head and back, white belly, and large orange-ish eyes perched on a twig.
A frog with a light green head and back, white belly, and large orange-ish eyes perched on a twig.

Where do species live?

It’s not a question that can be asked alone – we have to also ask how do we know where species live?, and that starts to get a bit more complicated. 

One of the most important types of data we can gather to understand where species live is species occurrence records, or points recording where a species was found complete with coordinates and a timestamp. Museum collections, scientific monitoring programs, and citizen science initiatives all contribute to collecting species records.

While each point is valuable on its own for the information it holds, the real strength of this data comes from the combination of thousands, even millions, of different records across thousands of species around the world. With access to this amount of data, scientists can better estimate what the true range of a species is, develop sophisticated distribution models for those species, and assess how those species ranges and populations are changing over time.

Increase in species records uploaded to GBIF since 2008 to 2024.

Several platforms exist for aggregating species records, but the largest is the  Global Biodiversity Information Facility, or GBIF , which is the standard platform in the biodiversity field for uploading species records. Since GBIF was established in 2001, the number of records it holds has exploded,  surpassing one billion in 2018  and exponentially growing ever since, hitting 2 billion records just four years later. This growth can be attributed in part to increased stipulations for the collection and sharing of biodiversity data, wider use of citizen science platforms, and new technologies like camera traps.

The need for robust datasets of species records has also been established in the Kunming-Montreal Global Biodiversity Framework (GBF). Target 21 of the GBF calls for “Ensur[ing] that the best available data, information and knowledge [about biodiversity] are accessible to decision makers, practitioners and the public.” While not the flashiest of the targets, the success of Target 21 is crucial to the success of many others – how can countries and other actors make informed conservation decisions about where to protect, where to restore, and where to allocate resources if we don’t know where species live?

So, we’ve established that we need more data on species records, but quantity by itself isn’t enough. If most records are coming from the same places and the same species, we're not necessarily getting new information. Currently, global species records datasets tend to be biased toward places with higher human populations and protected areas that are well-studied and frequently visited by tourists. 

We need data on as many species across as many taxonomic groups as possible, not just a few charismatic and well-studied species; we need data that covers as much of the expected range of a species as possible, not just a few small areas; and we need data over multiple years. 

This means we need a way to assess how well our existing data meets these criteria and strategically plan future monitoring efforts to target the largest data gaps and biases in order to support planning efforts such as those used by the  Half-Earth Project .

The Species Information Index

The Species Information Index (SII) was formulated to do just that. The SII is a biodiversity indicator that assesses the taxonomic, spatial, and temporal coverage of publicly available species occurrence records. It was introduced by  Oliver et al. (2021)  and is maintained by the  Map of Life  and supported by the  E.O. Wilson Biodiversity Foundation .

The calculation begins at the level of a single species.

The Species Information Score

For each species, we find the Species Information Score (SIS) annually by determining what portion of the expected distribution of that species contains a documented record from GBIF or eBird. The expected distribution is the best characterization currently available on Map of Life for that species. Currently, we calculate SIS using range maps developed by experts, but species distribution models could also be employed.

Let’s look at the lesser-snouted tree frog (Scinax nasicus) as an example.

The lesser-snouted tree frog lives in South America, where its expected range map covers an estimated 2.5 million square kilometers. In 2023, there were 42 documented records for this species. 

Slide the map to the left to see a simplified version of how the SIS calculation is done. 

Species Photo: Martin Arregui via iNaturalist, CC BY-NC. Species Records: GBIF.org (26 April 2024) GBIF Occurrence Download https://doi.org/10.15468/dl.dprz5w. Range Map: IUCN (2022). International Union for Conservation of Nature - Red List of Threatened Species. https://www.iucnredlist.org. Accessed on August 2022. Basemap: ESRI Light Gray.

First, we overlay a standard grid onto the expected distribution and records. We count the number of grid cells that overlap the expected distribution and the number of those cells that contained an occurrence record in the given year. The ratio of these two values gives us the global SIS. For the lesser-snouted tree frog, of the 256 grid cells of its expected distribution, 17 contained a record in 2023, giving it a global SIS of 6.6. So, about 6.6% of its population distribution is documented with primary species records. We can run this same calculation annually to explore how this SIS has changed over time.

Note that here, we're showing a simplification of this calculation – in reality, there is an additional layer of weights applied to certain grid cells based on the proportion of the range within the cell and overlap with multiple countries.

We just found the global SIS of the lesser-snouted tree frog, but we can also calculate this value separately for each country the species occurs in. About 17%, or 14 out of the 82 grid cells that occur in Argentina for this species, contain a record. That gives us an SIS of 17. Of the 94 grid cells of its expected distribution in Brazil, only 3 contain an occurrence record, leading to an SIS of 3.2. Swipe between the maps below to see the calculation for this species in the two countries.

Species Photo: Martin Arregui via iNaturalist, CC BY-NC. Species Records: GBIF.org (26 April 2024) GBIF Occurrence Download https://doi.org/10.15468/dl.dprz5w. Range Map: IUCN (2022). International Union for Conservation of Nature - Red List of Threatened Species. https://www.iucnredlist.org. Accessed on August 2022. Basemap: ESRI Light Gray.

Country-level Indicators

From here, we can now aggregate individual species scores to determine a country’s Species Information Index (SII). The National SII averages the national scores of all the species. We. can also calculate the Steward's SII, which adds the extra consideration of the stewardship each country has over a particular species, or the portion of the global expected distribution within that country. This up-weights species with a higher portion of their distribution in the given country – for example, endemic species get a stewardship weight of 1 because the entirety of the species' expected distribution occurs only in that one country. The Steward's SII therefore prioritizes species that are more unique to a given country. Finally, we can also look at the average SII across different taxonomic groups.

There are some striking patterns in this map: namely, some of the most species-rich places in the world also have some of the lowest SIIs. This is partly due to the fact that countries with a higher number of species have a larger burden of data coverage to attain, and partly because financial and other resources from comparatively species-poor developed countries have thus far been inadequately routed to species-rich developing countries. Target 19 in the GBF directly calls for increasing this allocation of resources to biodiversity monitoring, data collection, and in-country conservation support to at least $20 billion per year by 2025 and $30 billion per year by 2030. Such an accomplishment could not only help countries significantly improve their national SII through establishing more robust monitoring systems, but could also be a step towards attaining global justice for countries and people that have been exploited for resources by the Global North and are facing environmental crises disproportionate to their level of consumption and emissions.

The SII In Action

Consistent and thorough national reporting is a key measure of GBF success. The SII allows countries to pinpoint spatial and taxonomic gaps in species data coverage, track their monitoring success over time, and inform the most effective next steps for improving species monitoring and conservation efforts.

A key feature of the SII is that, while we run standardized global calculations at the Map of Life, countries and other conservation actors can tailor these same calculations to their own national datasets.

Input data

At the Map of Life, we only utilize publicly available species records from GBIF and eBird for SII calculations, but a national biodiversity agency may have access to several private datasets of species records. In addition, national entities may have access to more up-to-date or accurate expected range maps for species within their countries that are not available at the global level. Whereas our workflows must be standardized at the global level to ensure equal comparison among countries, national entities can leverage their own unique datasets to run more detailed calculations to inform internal conservation decision making.

Taxonomic scope

At the Map of Life, we run SII calculations only for the terrestrial vertebrate taxonomic groups – birds, mammals, reptiles, and amphibians – because these groups have high-quality expected range maps available for most species. A similar quality and coverage of data may be available at regional and national scopes for other groups, so national entities with access to this data can expand the SII calculations to a broader taxonomic scope.

Aggregation level

Here, we showed how the national SII is calculated from aggregated species-level scores. This same aggregation process can also occur at sub-national levels, such as at the level of provinces or states and even protected areas, by national entities who seek a more detailed analysis of internal species monitoring efforts.

This level of flexibility is a significant component of the SII that allows countries and other conservation actors to leverage the indicator for the most detailed, most accurate, and broadest scope of analysis possible. While an ultimate goal for all biodiversity data is public sharing (such as uploading to GBIF) to facilitate data access to all conservation actors – decision makers, scientists, and community members and the public alike – data privacy concerns remain salient, especially for national entities who seek to protect sensitive information about endangered or exploited species. We will maintain flexibility about the level of data sharing associated with the SII and related indicators, depending on the sensitivity of different species, locations, and situations.

On the Horizon

Black and white image of what appears to be a coyote at nighttime looking back at the camera trap that snapped their picture, mouth opening and eyes glowing.

Another layer of flexibility of the SII is the ability to intake new forms of data as conservation technology and efforts continue to advance in the coming years. For example, the last few decades have shown rapid advancements in camera trap technology, innovations in machine learning algorithms for species identification from photos, and the development of global platforms for aggregating and analyzing camera trap data, notably  Wildlife Insights . As a result, there has been a huge increase in the number of species records collected by camera trapping projects. In fact, one recent study by  Oliver et al. (2023)  found that incorporating species camera trap data from Wildlife Insights into SII calculations significantly increased the spatial and temporal coverage of birds and mammals compared to using GBIF data alone.

Other Target 21 Indicators

The SII is a component indicator of Target 21 of the GBF along with two other indicators: Participation in decision-making of indigenous peoples and local communities in the implementation of the Convention at all levels, and the Index of Linguistic Diversity. The former is maintained by the  Indigenous Navigator , a resource developed by Indigenous peoples for Indigenous peoples to collect and monitor data on the recognition and implementation of their rights. The latter is maintained by  TerraLingua  and quantitatively measures global trends in linguistic diversity. Together, these three indicators form a strong framework of data needs, covering both spatial biodiversity and cultural, social, and rights data. 

More Reading and Exploring

To learn more about the Species Information Index, read the introductory paper  Oliver et al. (2021)  and head to the  Map of Life SII page , where you can keep exploring national SII. Species-level scores will be added soon.


Species Information Index updates and development of this StoryMap were supported by the  E.O. Wilson Biodiversity Foundation .

StoryMap developed by Tamara Rudic with input and data processing help from Claire Hoffmann, Julia Portmann, Danyan Leng, Alex Killion, and Walter Jetz.

Species Information Index: Original Paper

Oliver RY, Meyer C, Ranipeta A, Winner K, Jetz W (2021) Global and national trends, gaps, and opportunities in documenting and monitoring species distributions. PLoS Biol 19(8): e3001336. doi.org/10.1371/journal.pbio.3001336

Species Information Index: Data and Maps

Increase in species records uploaded to GBIF since 2008 to 2024.

Species Photo: Martin Arregui via iNaturalist, CC BY-NC. Species Records: GBIF.org (26 April 2024) GBIF Occurrence Download https://doi.org/10.15468/dl.dprz5w. Range Map: IUCN (2022). International Union for Conservation of Nature - Red List of Threatened Species. https://www.iucnredlist.org. Accessed on August 2022. Basemap: ESRI Light Gray.

Species Photo: Martin Arregui via iNaturalist, CC BY-NC. Species Records: GBIF.org (26 April 2024) GBIF Occurrence Download https://doi.org/10.15468/dl.dprz5w. Range Map: IUCN (2022). International Union for Conservation of Nature - Red List of Threatened Species. https://www.iucnredlist.org. Accessed on August 2022. Basemap: ESRI Light Gray.